1. Field of the Invention
The invention relates to a process for producing an early warning signal of slick conditions in a system for easy warning of slick road conditions as well as a process for the provision of at least one virtual measuring station in a system for early warning of slick road conditions. The invention further relates to a warning device for slick road conditions having at least one, automatic measuring station and at least one evaluating device as well as a process and a warning device for slick road conditions.
2. Discussion of the Background Information
Early warning of slick conditions is understood to mean the short-term forecast of icing on roads and bridges. The purpose of this early warning is the specific preventive use of the "scattering" service or automatic melting agent spray apparatus for avoiding hazardous road conditions.
Currently, the early warning of slick conditions is carried out for predetermined points in the road system at which measuring stations with active or passive probes are provided, which stations detect the initial formation of slick conditions. Thus, probes are provided in particular for the air temperature, the ground temperature, the moisture on the roadway, and the precipitation, as well as probes for the freezing temperature of the liquid present on the roadway. The readings of the probes are transmitted to an evaluating device that derives an alarm announcement from the measured values. The early warnings of slick conditions are thus limited to short selected sections of the road on which the measuring stations are arranged. An extension of the early warning of slick conditions to more sections of the road requires the installation of more measuring stations, such that reasons of cost hinder the per se desirable extensive coverage of the road system with measuring stations. It has therefore been proposed to achieve a broad-coverage early warning of slick conditions by recording information on the entire road system by thermography and to derive an early warning of slick conditions therefrom. In order to achieve broad-coverage early warning of slick conditions, the surface temperature of the road surface is thermographed in the entire road system on three different nights with different weather conditions. This yields three characteristic temperature profiles that show "cold" or "warn" sections of the road. These profiles are invoked for spatial interpolation of the present state of the roads outside the measuring station. This method has disadvantages. First, the number of temperature profiles is not nearly sufficient to cover all weather situations and times of day, which is tantamount to a coarse simplification of the interpolation, which can lead to loss of information throughout. Secondly, the dynamics of heat and moisture exchange are not taken into consideration, since each thermal cartogram is necessarily a snapshot of the road conditions. The danger of slick conditions on a road section, however, depends on the previous weather conditions.